Mycotoxins are a broad class of toxic materials produced by the growth of fungi on foods. Aflatoxin is a specific mycotoxin produced by the action of a fungi belonging to the genus, Aspergillus, on grain, seeds, kernels or nuts. Aflatoxin contamination is particularly a problem in the peanut industry. In addition, aflatoxin can affect grains such as corn and hops, oilseeds, such as cottonseed, soybean, almonds, brazel nuts, pecans, pistachios, etc. The growth of fungi which produce aflatoxin is favored under the same conditions which are good for growing nuts and grains.
High levels of aflatoxin in foods presents a threat to animals and humans since aflatoxins at high levels have been shown to cause cancer in laboratory animals. For this reason, the USDA has set limits on the amount of aflatoxin and other mycotoxins that can be in food products.
There have been attempts to detoxify aflatoxin-contaminated food sources, but in general these have had very limited success, often with undesirable side effects, either flavor degradation or destruction of the food itself. Therefore, the general treatment of aflatoxin-contaminated material is to attempt to separate the aflatoxin-contaminated material from the uncontaminated materia. Alfatoxin contamination occurs within single grains, kernels, nuts, or peanuts. Therefore, removal of contaminated materials is usually done by sorting using an optical detector and also by manually removing damaged nuts. However, this method is not good for detecting aflatoxin-contaminated whole nuts which do not in any way appear to be damaged.
One method of color sorting is described in U.S. Pat. No. 4,035,518 in which aflatoxin-contaminated grains, corn and nuts are contacted with an aqueous solution containing a water soluble, food-compatible aflatoxin agent at elevated temperatures for a short period of time. The nuts are then washed with water. The aflatoxin agent causes the aflatoxin-contaminated nuts to undergo a sharp, almost immediate visual change. The nuts are then sorted by color. Aflatoxin agents are generally alkaline materials such as potassium hydroxide, sodium hydroxide, etc.
Generally, the amount of contamination of a corn, grain, seed or nut product is measured by the parts per billion or parts per million aflatoxin in a sample of the product. If the parts per billion is below the acceptable limit for the end food use, the sample or lot of material will be processed. However, if sampling misses several highly contaminated materials, some of the final product could be very high in aflatoxin even though the lot sampled at low aflatoxin level. Also, sampling variations can cause basically good lots of grain, nuts or seeds to test high and be declared inedible. Therefore, a process which would separate contaminated nuts or grains, particularly those which appear to be undamaged, is highly valuable. This process would allow the separation of contaminated whole grains, nuts or seeds from other undamaged whole products, thus lowering the mycotoxin or aflatoxin level in the entire batch.
Surprisingly, it has been found that aflatoxin-contaminated seeds, grains or nuts have a lower specific gravity then uncontaminated seeds, nuts or grain. Therefore, the aflatoxin-containing nuts can be separated using a liquid flotation process. A highly preferred process is dynamic flotation. Such separation is accomplished under carefully controlled conditions so that the interior of the grain, kernels, seeds or nuts, whether or not they are contaminated, are not penetrated, to any great extent, with the specific gravity separation medium. This process provides a means to separate the individual contaminated whole kernels which may otherwise be missed.
Flotation has been used in the past to separate oils, seeds, husks and fruits from non-edible contaminants, i.e. stones, rocks, stems, etc. It has also bee used to separate oils from other materials. However, flotation does not appear to have been used to separate aflatoxin-contaminated seeds, kernels, nuts or grain from wholesome products.
It is an object of this invention therefore to separate mycotoxin-contaminated nuts, kernels, seeds and grains from uncontaminated nuts, kernels, seeds and grains using a liquid specific gravity separation process.
It is a further object to separate otherwise good appearing but contaminated nuts, seeds, kernels or grains from other non-contaminated products, thus lowering the overall mycotoxin level of the product.
These and other objects will become apparent from the description of the invention.